#include <fstream>
#include <iostream>
#include <string>

using namespace std;

void swap(int &a, int &b)
{
    int temp = a;
    a = b;
    b = temp;
}
 
int main()
{
    int a = 10;
    int b = 20;
    swap(a, b);
    cout << "a = " << a << ", b = " << b << endl;

    int &c = a;
    cout << "c = " << c << endl;

    c = 30;
    cout << "a = " << a << ", b = " << b << endl;
}
